Burgess Shale type fossils found
with Trilobites of the Wheeler Formation:

The
Drum Mountains portion of the Wheeler are shallow facies and is equivalent to
the Pierson Cove Formation. The Elrathia in the Drums are for the
most part Elrathia marjumi, although some appear to be an intermediate
species between Elrathia marjumi and Elrathia kingii. There is
much debate on where the boundary between the Pierson Cove and the Wheeler
Formation actually is.